Influence of Fluid Dynamics on Heat Transfer in a Preswirl Rotating-Disk System

Modern gas turbines are cooled using air diverted from the compressor. In a “direct-transfer” preswirl system, this cooling air flows axially across the wheel space from stationary preswirl nozzles to receiver holes located in the rotating turbine disk. The distribution of the local Nusselt number Nu on the rotating disk is governed by three nondimensional fluid-dynamic parameters: preswirl ratio βp, rotational Reynolds number Reϕ, and turbulent flow parameter λT. This paper describes heat transfer measurements obtained from a scaled model of a gas turbine rotor-stator cavity, where the flow structure is representative of that found in the engine. The experiments reveal that Nu on the rotating disk is axisymmetric except in the region of the receiver holes, where significant two-dimensional variations have been measured. At the higher coolant flow rates studied, there is a peak in heat transfer at the radius of the preswirl nozzles associated with the impinging jets from the preswirl nozzles. At lower coolant flow rates, the heat transfer is dominated by viscous effects. The Nusselt number is observed to increase as either Reϕ or λT increases.